1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting liquid.
2. Description of the Related Art
Ink-jet (IJ) printers have recently been used not only for home printing but also for commercial printing, such as business printing and retail photo printing, and for industry printing, such as electronic circuit printing and panel display, and applications are spreading. Supporting high-speed printing is a strong requirement for IJ printer heads for use in commercial printing and industry printing. To meet the requirement, recording elements that generate energy for ejecting liquid ink are driven at high frequency, or a line head having a width larger than the width of a recording medium and having a large number of ejection ports is used.
PCT Japanese Translation Patent Publication No. 2010-521343 discloses a configuration of a long line head in which a plurality of recording element substrates are disposed in a staggered arrangement. The configuration disclosed in PCT Japanese Translation Patent Publication No. 2010-521343 achieves the size reduction of a head by disposing electrical wiring substrates only at a position facing first side portion of the recording element substrates. Examples of the electrical wiring substrates include a flexible printed circuit (FPC) and a tape automated bonding (TAB) circuit. The configuration including a plurality of recording element substrates sometimes use recording element substrates having a parallelogram planar shape to achieve the size reduction of the head and high-density printing.
The recording element substrates and the electrical wiring substrates are electrically connected using connecting members, such as bonding wires, to transmit and receive electrical power and electrical signals. The connecting members are generally sealed with a sealing member, such as a thermosetting resin, to prevent breakage due to an external force or corrosion due to liquid.
An invention disclosed in U.S. Pat. No. 6,609,786 provides a head module (unit) in which a recording element substrate and so on are mounted on an individual support member, and a plurality of the head modules are arranged in a line to form a long line head. The head modules disclosed in U.S. Pat. No. 6,609,786 have a rectangular planar shape. The head modules are inclined so that adjacent head modules are overlapped in a longitudinal direction and in a direction orthogonal thereto, thus achieving high density.
Of liquid ejection heads, recording element substrates having a parallelogram planar shape and the configuration in which at least first side portion of inclined recording element substrates, as disclosed in U.S. Pat. No. 6,609,786, is covered with a sealing member can cause relative misalignment due to cure shrinkage of the sealing member. The misalignment of the recording element substrates from proper positions can cause misalignment of the landing positions of ejected liquid, thus hindering good printing. This problem occurs not only in a line head having a plurality of recording element substrates, as disclosed in PCT Japanese Translation Patent Publication No. 2010-521343 and U.S. Pat. No. 6,609,786, but also in a compact liquid ejection head having only one recording element substrate that ejects liquid while moving, that is, a so-called serial head. In particular, a line head in which a plurality of recording element substrates are disposed, as disclosed in PCT Japanese Translation Patent Publication No. 2010-521343, causes the above problem in each of the recording element substrates and also a decrease in the ejection accuracy (landing accuracy) of liquid due to the decrease in the accuracy of the relative position of the recording element substrates. Using such liquid ejection heads in ink-jet printers would cause streaks and non-uniformity in an image formed by ejecting liquid, thus degrading the image quality. In particular, recent ink-jet printers form remarkably high-definition images and thus require eliminating even slight misalignment of the recording element substrates, which has not been a critical problem. Furthermore, in the configuration disclosed in PCT Japanese Translation Patent Publication No. 2010-521343, a plurality of recording element substrates are mounted on one long support structure, so that even one problem in the plurality of recording element substrate would make the entire head unavailable.
The configuration in which a plurality of independent head modules are provided, as disclosed in U.S. Pat. No. 6,609,786, also has the possibility that the positions of the recording element substrates in the individual head modules are misaligned variously. In such a case, the accuracy of the relative positions of all the recording element substrates cannot be increased unless the misalignment of the head modules is adjusted after the plurality of head modules are combined. Thus, its manufacturing process and adjusting work are complicated.